1. Field of the Invention
The present invention relates to a method for producing a multilayer laminated film, which comprises bonding first and second transparent films each having a moisture percentage of 0.5 to 5% by weight to both sides of a resin film having a moisture percentage of 10 to 60% by weight through an adhesive or pressure-sensitive adhesive layer interposed therebetween.
The production method of the present invention may be used to form a variety of multilayer laminated films. Specifically, the production method of the present invention may be used to form a polarizing plate, in which a polarizing film is used as the resin film, and transparent protective films for the polarizing film are used as the transparent films. The production method of the present invention may also be used to form other multilayer laminated films for use in wrapping food products, medical equipment and so on.
2. Description of the Related Art
A conventional process of bonding a transparent film to both sides of a resin film to form a multilayer laminated film generally has been used aqueous adhesives or pressure-sensitive adhesives. The method for bonding the transparent film to both sides of the resin film typically employs a simultaneous lamination method that includes feeding the resin film between a pair of rolls while feeding the transparent film to both sides thereof, and laminating them at the same time or employs a sequential lamination method that includes feeding the resin film between a pair of rolls while feeding the transparent film to one side thereof, laminating them, and then bonding the transparent film to the other side of the resin film.
If the resin film and the transparent film are laminated according to the above lamination method, however, bubbles can be formed between the resin film and the transparent film in the resulting multilayer laminated film. In addition, wrinkles or stripe-like irregularities can also be produced.
Concerning the problem of the production of wrinkles and so on, there is proposed a method including laminating a resin film (a polyvinyl alcohol film with a moisture percentage of 0.1 to 20% by weight) and a transparent film (a cellulose film) under a specific nip pressure (JP-A No. 10-166519). Even using this method, however, the production of bubbles cannot be sufficiently prevented between the resin film and the transparent film in the multilayer laminated film.